A frame with a unilateral vacuum bag with an integral seal arranged for sealing against a mould table flange corresponding to the frame is known in the background art.
FR2689809 describes a vacuum bag assembly for enveloping a composite lay-up between the two vacuum bags. The vacuum bag assembly is arranged for vacuum draping an external mould.
WO 01/41993 describes a double vacuum bag vacuum infusion process. The patent application describes a lay-up arranged between the vacuum bags, and further that the vacuum bags with the lay-up being draped over an external mould on a flat table.
EP1492664 describes a single sided vacuum bag frame for a lay-up in a mould.
A disadvantage related to the use of a single-sided vacuum bag is that it may be difficult to envelope the mould as a core in the composite product, and a consequence of this may lead to the requirement of conducting the moulding process twice for completing the two faces of the composite product. Another disadvantage of prior art is that the draping of composite fibres over the edge of the mould may be displaced with regard to the position of the fibres near the edge when using a single sided vacuum bag or an external mould. A composite having displaced fibres near the edge may be subject to uneven wear and may delaminate. A single sided vacuum bag or external mould may also result in a tension in the vacuum bag during vacuum pumping leading to a non-uniform pressure near edges of the mould, incurring corresponding undesired variation in matrix thickness.
A disadvantage of the vacuum bags according to background art is that the vacuum bag frames may be displaced during assembly and vacuum pumping. The double frames may also be displaced or disturbed during handling to and from the furnace.